The present invention relates to a switching converter having at least two converter stages connected in parallel.
To supply voltage and current to loads which draw a large amount of current, it is known practice to provide switching converters, which comprise a plurality of converter stages connected in parallel, each of which provides a portion of the current drawn by the load. In this case, the aim is to actuate the individual converter stages such that they each deliver the same output currents to the load in order to achieve an even distribution of current in the individual converter stages. Such converter stages are also called multiphase converters if the individual converter stages are actuated with offset timing.
To ensure such even distribution of current over the individual converter stages in a switching converter which comprises a plurality of converter stages connected in parallel, it is known practice, for example from GB 2 012 501 A, U.S. Pat. No. 6,404,175 B1 or US Published Application 2003/0048648 A1, to detect the output currents from the individual converter stages and to make a common current signal available on a bus to which all of the converter stages are connected. This current signal is dependent on the output currents from the individual converter stages and is used to actuate the individual converter stages. In the case of this design, the individual converter stages are additionally supplied with a signal that is dependent on the output voltage and that is used to regulate the output voltage from the individual converter stages. In this case, the output voltage is the voltage that is provided by the converter and that is present across a connected load.
In the case of another design for actuating the converter stages in a multiphase converter, which is described in US Published Application 2002/0036486 A1, for example, there is a common actuation circuit for the individual converter stages. The actuation circuit is supplied with a signal, which is dependent on the output voltage, and with current measurement signals from the individual converter stages. The actuation circuit uses these signals to generate actuation signals for the individual converter stages.
It is increasingly desirable for such actuation circuits to be in the form of digital circuits that process the current measurement signals and the output voltage signal digitally in order to produce actuation signals for the individual converter stages. This requires the use of analog/digital converters (A/D converters) for converting the current and voltage measurement signals, which are normally in the form of analog signals, into signals which can be processed digitally. In this context, one A/D converter is needed per converter stage. Such A/D converters, which convert an amplitude value of an analog signal into a measurement value that can be processed digitally, however, are complex to produce. The required complexity increases as the resolution of the A/D conversion increases and as the speed of the A/D conversion increases. Particularly in the case of the switching converters explained, which have a plurality of converter stages, great demands are placed on the accuracy/resolution and the speed of the A/D converters for converting the current measurement signals, which results in a high level of complexity and hence in high costs for such a system.